1. Field of the Invention
The present invention relates to a time-divisional driving organic electroluminescence display with pixels possessing an enhanced aperture ratio due to parallel alignment of the power supply lines and data lines.
2. Discussion of the Background
A time-divisional driving organic electroluminescence display supplies a driving current required for light-emitting action of a plurality of organic light-emitting diodes (OLEDs) through one driving transistor. The driving transistor can be coupled with a plurality of light-emission control transistors, which can each be coupled with an OLED. The light-emission control transistors coupled with the driving transistor are sequentially activated by sequentially transmitted light-emitting control signals, and the plurality of OLEDs emit light sequentially.
FIG. 1 shows a circuit diagram illustrating a time-divisional driving organic electroluminescence display according to the prior art.
Referring to FIG. 1, a red data line 100, a green data line 110 and a blue data line 120 are disposed parallel to each another, and a scan line 130 is disposed to cross the data lines.
A first pixel 140 is arranged near where the red data line 100 and the scan line 130 cross. The first pixel 140 comprises a red driving transistor compensation circuit 147, a red driving transistor TR, a capacitor CR, four light-emission control transistors TRE1, TGE2, TRE3, TGE4, and four OLEDs R1, G2, R3, G4, each coupled with a light-emission control transistor.
A second pixel 150 is arranged near where the green data line 110 and the scan line 130 cross. The second pixel 150 comprises a green driving transistor compensation circuit 157, a green driving transistor TG, a capacitor CG, four light-emission control transistors TBE1, TRE2, TBE3, TRE4, and four OLEDs B1, R2, B3, R4, each coupled with a light-emission control transistor.
A third pixel 160 is arranged near where the blue data line 120 and the scan line 130 cross. The third pixel 160 comprises a blue driving transistor compensation circuit 167, a blue driving transistor TB, a capacitor CB, four light-emission control transistors TGE1, TBE2, TGE3, TBE4, and four OLEDs G1, B2, G3, B4, each coupled with a light-emission control transistor.
The red driving transistor TR and the capacitor CR of the first pixel 140 are commonly coupled with a power supply line ELVDD, and power supply line ELVDD perpendicularly crosses with the red data line 100, which is arranged on a different layer than power supply line ELVDD. Power supply line ELVDD perpendicularly crosses with the green data line 1110 and the blue data line 120, which are both arranged on a different layer than power supply line ELVDD.
When a scan signal SCAN [n] is applied through the scan line 130, the scan signal SCAN [n] is received by the red driving transistor compensation circuit 147, the green driving transistor compensation circuit 157 and the blue driving transistor compensation circuit 167. A switching transistor provided at each driving transistor compensation circuit is turned on.
A red data signal Rdata is applied to a gate terminal of the red driving transistor TR and the capacitor CR through a switching transistor in the turned on red driving transistor compensation circuit 147, and the red data signal Rdata is stored in the capacitor CR. Similarly, a green data signal Gdata, applied through the green data line 110, is stored in the capacitor CG, and a blue data signal Bdata, applied through the blue data line 120, is stored in the capacitor CB.
The input terminal of driving transistor TR is coupled with power supply line ELVDD and the output terminal of driving transistor TR is commonly coupled with four light-emitting control transistors. The gate terminal of each light-emitting control transistor is coupled with light-emitting control signal lines, and the output terminal of each light-emitting control transistor is coupled with an OLED. Driving transistors TG and TB are similarly arranged.
Thus, when a first light-emitting control signal EMI[1] is activated, the light-emitting control transistors TRE1, TBE1, TGE1 are turned on, and the OLEDs R1, B1, G1 begin to emit light.
The light-emitting control transistors TRE1, TBE1, TGE1 are then turned off, and a new red data signal Rdata, a new green data signal Gdata and a new blue data signal Bdata are applied and stored in CR, CG, and CB, respectively. Next, a second light-emitting control signal EMI[2] is activated. The light-emitting control transistors TGE1, TRE2, TBE2 are turned on, and the OLEDs G2, R2, B2 begin to emit light.
The light-emitting control transistors TRE2, TBE2, TGE2 are then turned off, and a new red data signal Rdata, a new green data signal Gdata and a new blue data signal Bdata are applied and stored in CR, CG, and CB, respectively. Next, a third light-emitting control signal EMI[3] is activated. The light-emitting control transistors TGE3, TRE3, TBE3 are turned on, and the OLEDs G3, R3, B3 begin to emit light.
The light-emitting control transistors TRE3, TBE3, TGE3 are then turned off, and a new red data signal Rdata, a new green data signal Gdata and a new blue data signal Bdata are applied and stored in CR, CG, and CB, respectively. Next, a fourth light-emitting control signal EMI[4] is activated. The light-emitting control transistors TGE4, TRE4, TBE4 are turned on, and the OLEDs G4, R4, B4 begin to emit light.
Once all four sets of OLEDs have emitted light in response to applied light-emitting control signals, the above described sequence repeats. As described above, the light-emitting control transistors are sequentially activated, and the organic light-emitting diodes sequentially perform light-emitting actions by the sequentially activated light-emitting control transistors.
According to the foregoing prior art, the plurality of data lines and the power supply line ELVDD are arranged to perpendicularly cross each other. Furthermore, circuit layout may not be easily modified because the ELVDD line perpendicularly crosses the line connecting the driving transistor and the light-emitting control transistor.
Finally, reduction of an aperture ratio results from excess complexity in circuitry wiring. Particularly, the aperture ratio may be significantly reduced in a bottom emission device where a plurality of lines are disposed on the lower layer of the circuitry. Although narrowing a line may prevent the reduction in aperture ratio, the reduced line width may also create diminished transmission efficiency of a signal transmitted through the wiring. Additionally, reduced width of the power supply line ELVDD may result in increasing power noise of an organic electroluminescence display.